Acinar cell differentiation continues postnatally in the rat salivary glands and involves a cell proliferative growth period during its early stages. Cells which are undergoing division are passing through a cycle of events including DNA synthesis, visible mitosis, and the preparatory phases which preceed these periods. This cell cycle can be measured by use of autoradiography and provides a model by which one can study the effects of the autonomic innervation (parasympathetic and sympathetic) on the growth and development of the rat salivary glands (parotid, submandibular, and sublingual). This study will analyze the role of autonomic nervous system (A.N.S.) in the development of the salivary gland by stimulation and diminution of both sympathetic and parasympathetic branches. This will be done by the use of sympathomimetic, parasympathomimetic, sympatholytic, and parasympatholytic drugs as well as by actual surgical denervation procedures and chemical symphathectomy. The normal cell cycle curve of each of the major salivary glands will be used as a foundation upon which alterations produced by drug or surgical procedures may be determined. In addition to the measurements of the duration of the acinar cell cycles phases, thymidine labelling index, mitotic index, DNA, RNA, protein and incorporation of 3H-thymidine (scintillation counting) will be calculated in order to further elucidate the importance of both branches of the autonomic nervous system in cellular events. These experiments will provide a basic understanding of the role of the A.N.S. in the development of the rat salivary glands.